使用PHP邮件和密件抄送中的多个地址发送大型电子邮件列表时的个性化“收件人”字段

Im trying to remember a trick i was taught a while back but can not.

Basically, im using PHP mail() in this fashion:

$to = "emailAddress1@domain.com";
$subject = "Welcome to BuildSanctuary";
$messageContent = "Thankyou for registering Bla bla bla";
$message = 'SOME HTML EMAIL STUFF including the $messageContent var';
$headers = 'MIME-Version: 1.0' . "
";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "
";
// Additional headers
$headers .= 'To:' . "
";
$headers .= 'From: Accounts<accounts@domain.com>' . "
";
$headers .= 'Bcc: emailAddress1@domain.com,emailAddress2@domain.com,emailAddress3@domain.com,emailAddress4@domain.com' . "
";

// Mail it
mail($to, $subject, $message, $headers);

I got told a while back that there was a way that you could put your own email in the to field, but when the users receive the emails it looks like they were personally sent the email and the to field shows just their email.

Is this possible? Cant think how.

Thanks.